The present invention is similar to that disclosed in my copending application, U.S. Ser. No. 382,780, filed on May 27, 1982, now U.S. Pat. No. 4,479,749. The invention relates to apparatus for emptying railroad cars carrying bulk material by rotating them about their longitudinal axis to dump the contents over the sides of the cars into a hopper below. More particularly, it relates to such a rotary card dumper which incorporates an efficient, simplified dust collection system to contain the clouds of dust created by the dumping operation.
It is common practice to empty trainloads of bulk material by cycling the cars through a cylindrical frame which is rotated about a horizontal axis to dump the contents over the side of the car into a hopper underneath the rotatable frame. During the dumping operation billowing clouds of dust are usually created. While this was not considered a problem in earlier times, recent concern for the environment and for working conditions has resulted in steps being taken to contain these dust clouds. Under present practice, dust collectors are installed adjacent to the dumper structure on a separate foundation. This arrangement requires ducting of the dust ladened air from the hopper pit to the dust collectors as well as ducting of the cleaned air to the exhaust fans.
Because of the billowing nature of the dust clouds created during dumping, it is necessary that the duct system draws air into the openings around the hopper pit area at a rate which exceeds the dust capture velocity. That is, at a velocity which prevents puffs of dust from escaping through these openings and into the dumper building. This is difficult to achieve with the present ducted system and, in any event, requires large volume exhaust fans to maintain capture velocity across all of the air entrance areas. This in turn requires increased horsepower to satisfy duct losses which approach 50% of the designed horsepower requirement. The placement of the dust collectors on a separate foundation also requires that the dust collected in the dust collector hoppers must be transported back to the dumper pit through a maze of screw conveyors, rotary valves and chutes; all of which require constant maintenance. Some materials tend to cake which can plug up the system, especially at the screw conveyors, rotary valves and small ducts. Furthermore, the duct work which handles the dust ladened air is subject to wear at all points where the duct changes direction. These points also require frequent maintenance.